Conventionally, there is a known gasification furnace which is applied to a carbon-containing fuel gasification apparatus for gasifying a carbon-containing fuel such as coal. Examples of such gasification furnaces include a double-walled reactor called a tower-type reactor or a crossover-type reactor.
Typically, a pressure vessel housing a gasification furnace and a heat exchanger, which constitute a gasification furnace apparatus, is provided with an annular space (hereinafter called an “annulus section”) filled with an inert gas such as a nitrogen gas and maintained at a high pressure. That is, the gasification furnace apparatus is constituted of a gasification furnace wall forming a passage for an in-furnace gas, and the pressure vessel provided outside the gasification furnace wall and holding the pressure; the annulus section filled with an inert gas is provided between the gasification furnace wall and the pressure vessel in order to protect the pressure vessel from the high-temperature in-furnace gas.
As disclosed in Patent Literature 1, for example, the conventional gasification furnace apparatus is provided with an in-furnace pressure equalizing pipe, which communicates between the inside of the furnace and the annulus section, as a means for directly equalizing the pressures of the inside of the furnace and the annulus section. By directly equalizing the pressures of the inside of the furnace and the annulus section, this in-furnace pressure equalizing pipe allows the gasification operation to be continued in a stable manner even when the differential pressure between the inside of the furnace and the annulus section fluctuates. That is, the in-furnace pressure equalizing pipe functions to suppress increase in the difference in pressure (differential pressure) between the pressures inside the furnace and inside the annulus section in order to protect the gasification furnace wall.